BerryBoot is a tool / bootloader that allows you to install (and boot) multiple Linux distributions on the same SD card or USB drive. It supports Raspberry Pi as well as Android tablets, TV sticks and boards that have an Allwinner A10 processor, such as MK802.

Berryboot comes with a menu editor that allows you do add more operating systems, rename or delete existing Linux distributions and so on. You can also add your own custom operating systems to the menu - see the bottom of the Berrybot homepage for more info.

Using Berryboot is very easy: simply download the zip, extract it and copy the contents to the SD card, which must be formatted to FAT (you can use Gparted to format the SD card). Then start Raspberry Pi and follow the instructions: